Stabilization of vinyl polymers

ABSTRACT

NEW ORGANO-TIN COMPOUNDS, SUITABLE FOR USE AS STABILIZERS FOR VINYL HALIDE RESINS, ARE OBTAINED BY REACTING A DIALKYLTIN OXIDE, HYDROXIDE, OR DIHALIDE WITH A MONOESTER OF A DIOL OR AN ACYLOXY ALCOHOL WITH A MRCAPTO-ACID.

United States Patent 3,809,677 STABILIZATION OF VINYL POLYMERS Vincent Oakes, St. Helens, and Brian Rodney Iles, Liverpool, England, assignors to Interstab Limited, Liverpool, England No Drawing. Continuation of abandoned application Ser.

No. 193,158, Oct. 27, 1971, which is a division of application Ser. No. 877,857, Nov. 18, 1969, now Patent No. 3,665,024, dated May 23, 1972. This application Nov. 14, 1972, Ser. No. 306,207 Claims priority, application Great Britain, Nov. 22, 1968, 55,523/ 68 Int. Cl. C08f 45/62 US. Cl. 260-45.75 K 2 Claims ABSTRACT OF THE DISCLOSURE New organo-tin compounds, suitable for use as stabilizers for vinyl halide resins, are obtained by reacting a dialkyltin oxide, hydroxide, or dihalide with a monoester of a diol or an alkoxy or acyloxy alcohol with a mercapto-acid.

This is a continuation of copending application Ser. No. 193,158, filed Oct. 27, 1971, now abandoned, which in turn, is a divisional of copeuding application Ser. No. 877,857, filed Nov. 18, 1969, now Pat. No. 3,665,024, granted May 23, 1972.

This invention relates to the stabilization of vinyl polymers with organotin compounds, and to new organotin compounds suitable for use for this purpose.

Vinyl chloride polymers and copolymers are thermoplastic in nature and therefore have to be heated in order to soften them during fabrication operations such as calendering and extruding. Such heat is limited in degree and duration by the tendency of the resins to decompose. This decomposition leads to deterioration in the physical properties of the resin. It also results in severe darkening in color of the resin which prohibits its use in lightly colored or transparent articles. This latter property is obviously a major drawback to the use of PVC in many applications. -In order to overcome this, several products have been suggested as stabilizers. In general these fall into three main classes, namely: lead salts, barium/ cadmium soaps and organotin compounds.

Of these the organotin compounds are the most effective stabilizers, particularly when they contain tin sulphur bonds. Such products are commonly refered to as thiotins.

-In our British specification No. 1,027,781 we demon strated that advantages were to be gained by using dialkyltin salts derived from esters of triols or polyols with mercaptoacetic or beta-mercapto propionic acid. These salts were shown to be of particular advantage if there was at least one free hydroxyl group remaining in the ester from which the dialkyltin salt was formed. It was concluded that the free hydroxyl group had an important bearing on the course of the stabilization reaction although the manner in which it was effective was not known.

Products derived from esters of triols such as glycerol, trimethylol propane and polyols such as pentaerythritol, all suffer from one major drawback in that they can only be prepared as thick intractable products of a gummy plastic or elastomeric consistency. These difiiculties not only rendered the product unattractive from a sales and handling viewpoint, but also made them difiicult to manufacture with the required degree of consistency. Therefore although satisfactory products could be quite easily prepared in the laboratory it proved difiicult to reproduce them consistently at full production level. These difliculties are thought to arise because of the potential polymeric nature of the resulting compounds. It is the purpose of this invention to provide a type of compound which is at least as good in performance as those described in British Specification No. 1,027,781, but does not suffer from the same handling and manufacturing difliculties of these compounds.

According to the invention, vinyl resins are stabilized by incorporating therein products obtained by reacting a dialkyltin oxide, hydroxide or dihalide with a monoester of a diol or an alkoxy or acyloxy alcohol with a mercapto-acid.

Examples of suitable diols are ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol. Suitable alkoxy alcohols include Z-methoxy-ethanol. Suitable acyloxy alcohols include 2-acetoxyethanol. Suitable mercaptoacids include mercapto-acetic acid (also known as thioglycolic acid) and beta-mercaptopropionic acid. The di alkyltin compounds may have alkyl groups of up to 10 carbon atoms, especially butyl or octyl groups.

The facts that the free hdryoxyl group of a diol ester can be replaced by an alkoxy group or an acyloxy group, and that compounds derived from diols such as diethylene glycol are very eifective appears to indicate that the effective part of the molecule is the oxygen atom and not the free hydroxyl group. It is therefore thought that all types of alkoxy and acyloxy groups would be suitable as well as free hydroxyl groups. This would have the additional advantage that the production of thick intractable compounds would be virtually impossible.

An additional advantage of the new products is that they appear to be universally applicable to the difierent types of PVC available. There are two principal typeset PVC available. The first of these is made by a suspension polymerization process and the second by an emulsion polymerization process. The two types of PVC differ markedly in their handling and stabilization characteristics. The new products described appear to be equally effective in both types of PVC and in this manner difier from products which have been described earlier.

The stabilizers according to the invention may be used in quantities of from 0.5% to 10% based on the weight of the vinyl resins.

The products of this invention can be prepared for example by reaction of the dialkyltin oxide with the mono-mercapto ester of the selected glycol or alcohol, or by reaction of a dialkyltin halide with the sodium salt of the ester.

The invention is illustrated by the following examples:

EXAMPLE 1 The selected glycol or alcohol (1 mol) and thioglycolic acid (1 mol) were refluxed together in toluene (150 ml.) in an apparatus fitted for azeotropic distillation and the reaction continued until water (1 mol) had been collected. The toluene was then removed under reduced pressure in a rotary evaporator, the ester being obtained in quantitative yield. This ester (1 mol) was then heated to C. and dibuyltin oxide (0.5 mol) added slowly with stirring. When all had dispersed the temperature was increased to C. and held there until all the water of reaction had been removed. The product was then filtered, using a filter aid, to atford the desired salt in approximately 98% yield in each instance.

Using this general technique the following compounds were prepared, each of which is thought to be a new compound.

Compound Dibutyltin bis (ethylene glycol B mercapto propionate) Bu;Sn(SCH;CH(J-0 CH CH OH);

Dioctyltin-bis-(ethylene glycol thioglycollate) II OctnSn SCHaC 0 CHaCHzOH):

Dibutyltin-bis-(triethylene glycol thioglycollate) Bu Sn(SCH(J O (CHiCH OhCHQCHiOH):

Dibutyltin-bis-(1,4-butylene glycol thioglycollate) O BugSIKSCHn O CH CHzCH CHzOH),

EXAMPLE 2 Di-n-butyltin oxide (24.8 g.) was dissolved in acetic anhydride (102 g.) at 8090 C. to form dibutyltin diacetate. Ethylene glycol thioglycollate (272 g.) was added, and the mixture was distilled under reduced pressure, until no more acetic acid distilled ofi. The product was filtered to yield dibutyltin-bis-(ethylene glycol thioglycollate) in high yield.

EXAMPLE 3 Organotin compounds can be used for the stabilization or both rigid and plasticized P.V.C. The most rigorous examination is to test them in a rigid compound. This may be applied by compounding the stabilizer in the following formulation:

Suspension PVC 100 Lubricant 1 Stabilizer 2 taken from the rolls at a thickness of approximately 50 thou. Samples of this sheet are then heated in a laboratory air circulation oven at a temperature of 185 C., and inspection samples withdrawn at ten minute intervals. The rate of degradation of the PVC sheet can be observed quite readily from the rate of color formation in the samples. Using this technique, the following results were obtained, the first three compounds being known compounds used for the comparison with the products of the invention:

Time to color formation mins.)

Slight Product yellow Yellow Black Dlbutyltin-bis-(octyl thloglycollate) 30 60 Dioctyltin-bis(octyl thioglycollate) 80 70 90 Dibutyltin-bis-(glyceryl thioglycollat 60 70 80 Dibutyltin-(glyceryl-bis-thioglycollate) 65 75 Dibutyltin-bis-(ethyleue glycol thioglycollat 70 80 Dibutyltin-bis-(propylene glycol thioglycollate) 65 75 90 Dibutyltin-bls-(2meth0xy ethyl thioglycollate) 70 80 90 Dibutyltin-bis-(ethylene glycol B mercapto propiouat 70 8O 90 Di buty1t1n-bis-(triethylene glycol thloglycollat 50 60 8 Dibutyltin-bis-(1,4-butylene glycol thiocollat 60 70 90 Dioetyltin-bis-(ethylenc glycol thloglycollate) 60 80 90 EXAMPLE 4 In a similar manner to Example 3, the same stabilizers were examined in the following formulation:

Emulsion PVC 100 Lubricant 1 Stabilizer 2 the same known compounds being used for comparison of the results obtained.

It should be noted that when using this test with emulsion PVC, appearance of initial color takes place earlier but the development of color is more gradual. The colors are also somewhat different to those obtained with the suspension polymer. For this reason both tables should not be compared.

Time to color formation (mius.)

Slight Product yellow Yellow Amber Black Dlbutyltin-bis-(octyl thloglycollat 45 60 70 80 Diootyltin-bis-(octyl thioglycollate 45 70 80 90 Dibutyltin collate). 20 60 80 100 Dibutyltin collat 20 60 80 100 Dibut yltin-b thioglycollate) 60 90 110 Dibutyltln-bis-(propyle thioglycollate) 60 80 90 110 Dibutyltin-bis-(Z-methoxy ethyl thioglycollate) 70 85 95 -Dibutyltin-bis-(cthylene glycol 6 mercapto propionate) 20 6O 80 100 Dibutyltiu-bis-(triethylene glycol thioglycollate) 20 60 80 100 Dibutyltin-bis-(1,4-butylene glycol thioglycollate) 50 70 80 90 Dioctyltin-bis-(ethylene glycol thioglycollate) 60 80 90 100 What is claimed is:

l. A resin composition comprising a polymeric vinyl halide resin and a stabilizer in the amount of from 0.5% to 10% by weight of the resin, said stabilizer having the formula 5 r 6 wherein References Cited R is an alkyl group having up tq 10 carbon atoms; UNITED STATES PATENTS R2 is an alkylene g p having p to 5 carbon m 3,398,114 3/1963 Pollock 260 45 75 .(CH CH O) CI-I CH or 5 3,525,761 8/1970 Seki et a1 260-4575 CH CH(CH )OCH CH(CH and 3,525,760 8/1970 Seki et a1 26045.75 =1 or 2. n 2 A T l d l 1 h DONALD E. CZAJA, Primary Examiner rencomolona a1me nca wee 2 is S1 p S l s c l r l V. P. HOKE, Assistant Examiner 

